Nanodiamond Turns Into a Light Source

The scheme of obtained active nanodiamond antenna with nitrogen-vacancy centers. (Source: ITMO)

A research group from ITMO Univer­sity in Saint Peters­burg first time in the world developed a controlled light source based on nano­diamond. Experiments have shown that diamond shell doubles the emission speed light sources and helps to control them without any additional nano- and micro­structures. This was achieved due to arti­ficially created defects in a diamond crystal lattice. Obtained results are important for the develop­ment of quantum computers and optical networks.

One of the key areas of modern nano­photonics is the design of active dielectric nano­antennas or controlled photonic sources. As a base for nano­antennas scientists usually use plasmonic metal nano­particles. However, optical loss and heating of these particles encourages scientists to look for alternatives. For example, the researchers actively develop dielec­tric nano­photonics: they create nano­antennas based on perovskites and silicon. Recently, members of Inter­national Laboratory for Nano­photonics and meta­materials of ITMO University developed a new concept of active dielectric nano­antennas based on nano­diamonds.

Nano­diamonds are carbon nano­structures with unique properties. They have a sufficiently high refractive index, high thermal conduc­tivity and low inter­action activity. The scientists used nano­diamonds with nitrogen-vacancy centers (NV-centers). They are created arti­ficially by removing carbon atoms from the diamond crystal lattice. Opened vacancy is then linked to an implanted nitrogen atom. The electron spin of such NV-center is easily controlled by light, so that using that electron spin you can record quantum infor­mation.

The scientists studied optical properties of nano­diamonds and found that their radiation can be enhanced by combining the NV-center lumines­cence spectrum with optical Mie resonances of diamond nano­particles. This can be achieved at a certain position of the NV-center and the appropriate particle size. This way one can increase a nano­diamond Purcell factor. This indicator is used to estimate how a diamond shell affects the rate of sponta­neous emission of the light source. If the Purcell factor increases, the lumines­cence fading time reduces while the signal itself becomes stronger and much easier to read.

The scientists emphasize that this effect is achieved by using only proper­ties of nano­diamonds. “Usually, to accelerate the radiation, one has to create a complex system of resonators. But we managed to achieve similar results without any additional structures. We showed experi­mentally that the lumines­cence fading can be speeded up at least two times, using just simple physics,” says Dmitry Zuev from The Inter­national Labora­tory for Nano­photonics and Meta­materials.

In fact, experiments were carried out on nano­diamonds with multiple NV-centers. Even though the researchers also developed a theo­retical model for the behavior of single photon sources in the diamond shell. Calcu­lations showed that the speed of light emission can be increased by several dozen times. “Today getting a single photon from one NV-center in a nano­antenna is a rather difficult task. In order to implement such active nano­antenna in logic elements, for example, you need to manage their emission. In perspec­tive, our concept will help to effectively manage single photon emission sources. It is very impor­tant for the development of quantum computers and optical communi­cation networks,” notes Anastasia Zalogina, a member of the Inter­national Laboratory for Nano­photonics and meta­materials. (Source: ITMO)

Reference: A. S. Zalogina et al.: Purcell effect in active diamond nanoantennas, Nanoscale, online 17 April 2018, DOI: 10.1039/C7NR07953B

Link: International Laboratory for Nanophotonics and Metamaterials, ITMO University, St Petersburg, Russia 

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